It has long been assumed that one's susceptibility to psychiatric disorders is derived from inheriting specific gene alleles from one's parents and from one's personal experiences. However, recent publications, including those from my lab, raise the possibility that another component of susceptibility is from one's parents' experiences, the effects of which are transmitted to their offspring through non-Mendelian mechanisms that remain poorly understood. A particularly striking example is transmission through the paternal lineage, even when the males have no interaction with the mother during pregnancy or with offspring after birth. This grant proposal is driven by our recently published study demonstrating that chronic social instability beginning during adolescence causes enhanced anxiety and defective social interactions specifically in females across at least 3 generations. Remarkably, the phenotype is transmitted through the paternal lineage, even though male offspring do not display these phenotypes. Recent studies have shown that in addition to delivering DNA to oocytes upon fertilization, sperm introduce miRNAs that influence embryo development presumably by altering specific sets of early embryonic genes. Our new unpublished data implicate stress-induced changes in two sperm miRNAs as possible mediators of this phenomenon because they change not only in stressed males but also in their F1 and F2 male offspring that were not exposed to stress but transmit stress phenotypes to their female offspring. Moreover, we have identified potential mediators of stressed-induced behaviors that occur specifically in adult females by detecting elevated levels of both RCAN1, an inhibitor of calcineurin and a known inducer of anxiety, and the NFATc1 transcription factor, a promoter of RCAN-1 gene expression, in the hippocampus of both F1 and F2 offspring of stressed fathers. The first aim of this grant will reveal the specific roles played by these sperm miRNAs, as well as newly identified RNAs, in transmitting specific stress-induced behavior abnormalities to females across generations. In addition, it will test whether sperm miRNA changes and the ability to transmit stress phenotypes across generations are blocked by exposure of stressed males to an enriched environment and/or antidepressants. The second aim will reveal how social instability-induced changes in sperm RNAs lead to altered regulation of genes in female offspring that mediate their enhanced anxiety and defective social interactions. Overall, this proposal will deepen our understanding of the mechanisms underlying this newly revealed form of inheritance in mice that may also contribute to the heightened susceptibility of females to stress-associated psychiatric disorders.